Mobile phone has been popularized to the general public in recent years. The conventional mobile phone supported only basic voice communication. Then the mobile phone evolved to such a degree to support short messaging and multimedia messaging functions. Recently, so-called smartphone is widespread in use. The smartphone allows the user to enjoy various functions such as web-surfing, game, and map services. In order to make a full use of the functions of the smartphone, high-speed data communication is inevitable.
Recently, the 3Rd Generation Partnership Project (3GPP) has ratified significant parts of Long Term Evolution (LTE) standard. Besides, some countries have started to offer commercial LTE services. The LTE communication technology supports data communication at a data rate higher than that of Wideband Code Division Multiple Access (WCDMA). In the following, the description is directed to the communication method complying with the LTE standard. However, the present invention may be applied to other communication technologies as far as not departing from the nature of the present invention.
In the LTE communication technology, Radio Resource Control (RRC) protocol is used for radio resource allocation to the users. The RRC protocol is used in the procedure of allocating radio resource to the users and withdrawing the resources from the users who have been allocated the radio resources but not uses the resources any longer.
The RRC protocol is the protocol for use in managing the radio resource to be allocated to the terminals (User Equipment; UE) within the cell. According to the RRC protocol, the UE may be in one of two states. RRC_IDLE state is the state where the UE is not allocated any radio resource from the base station or the connection between the UE and the base station has been released. RRC_CONECTED state is the state where the UE has been allocated radio resource from the base station. In the RRC_CONNECTED state, the UE and the base station may transmit data in downlink (DL) or uplink (UL).
FIG. 1 is a diagram illustrating a connection and connection release procedure between a base station and a terminal in the conventional method. As described above, the terminal may be in one of the RRC_CONNECTED state 120 and RRC_IDLE state 110. The terminal is in the RRC_IDLE state initially. At a time point 130, the terminal receives an incoming call. If the incoming call is received, the terminal has to be allocated radio resource from the base station for data communication to transition to the RRC_CONNECTED state. Although the description is directed to the exemplary case of incoming call, the terminal has to transition to the RRC_CONNECTED state in other cases requiring data communication such as requesting a webpage in response to the user's manipulation. The terminal transitions to the RRC_CONNECTED state after executing the operation for connecting to the base station during the call setup time 140. If the terminal communicates data in the RRC_CONNECTED state, it may transmit/receive data without configuration of Resource Block (RB).
However, the terminal in the RRC_CONNECTED state occupies the large resource as compared to the terminal in the RRC_IDLE state. Accordingly, if a large number of terminals served by the base station are in the RRC_CONNECTED state, this may causes call drop or call block problem due to the resource shortage. Thus, the terminals which have not perform data communication over a predetermined duration have to transition to the RRC_IDLE state. In order to accomplish this, the base station triggers an RRC inactivity timer at the time 150 right after transmitting the last data packet 190 at the time 160. If no data communication occurs before the expiry 180 of the RRC inactivity timeout 170 configured at the RRC inactivity timer, the base station sends the terminal an RRC Connection Release message to release the RRC connection. As a consequence, the terminal transitions to the RRC_IDLE state.
FIG. 2 is a flow diagram illustrating the connection and connection release procedure between the base station 210 and the terminal 205 according to the convention method.
The terminal 205 sends the base station 210 a random access preamble at step 220. The base station 210 sends the terminal 205 a random access response in reply to the random access preamble at step 225. The terminal 205 sends the base station 210 an RRC Connection Request (RRCConnectionRequest) message at step 230. The base station 210 sends the terminal 205 an RRC Connection Setup (RRCConnectionSetup) message in correspondence to the RRC Connection Request message at step 235. The terminal 205 sends the base station 210 an RRC Connection Setup Complete (RRCConnectionSetupComplete) message at step 240.
The base station 210 sends the terminal 205 a Security Mode Command (SecurityModeCommand) at step 245. The terminal 205 sends the base station 210 a Security Mode Complete (SecurityModeComplete) message at step 250. The base station 210 sends the terminal 205 an RRC Connection Reconfiguration (RRCConnectionReconfiguration) message at step 255. The terminal 205 sends an RRC Connection Reconfiguration Complete (RRCConnectionReconfigurationComplete) message at step 260. Through the procedure to step 260, a connection is established for data communication.
The data communication is performed at step 265. For the expiry of the timeout 180 of FIG. 1 or other reasons, it may be requested to release the connection between the terminal 205 and base station 210. In this case, the base station sends the terminal 205 an RRC Connection Release (RRCConnectionRelease) message at step 270. As a consequence, the connection between the terminal and the base station 210 is released, and the terminal 205 enters the RRC_IDLE state to return the occupied resource.
The smartphone user has various traffic patterns. Particularly, the user of the legacy feature phone instead of smartphone generates significantly low traffic as compared to the smartphone user. Although using the same smartphone, the different traffic patterns may be generated depending on the application installed in the smartphone. The traffic pattern may be influenced by various factors such as time and place. For example, the traffic is likely to increase in the daytime rather than nighttime when people are sleeping. Like this, the traffic pattern may vary depending on the time and place. The conventional RRC protocol applies the RRC inactivity timer set to a fixed time (timeout) to all terminals without consideration on the traffic pattern per user.
With the popularization of the smartphone, the use of the social networking applications such as Social Network Service (SNS) or Instant Messenger is widespread. These applications transmit keep-alive messages periodically for push services. The keep-alive message is small in size (1 KB) but transmitted frequently. For this reason, the terminal establishes and releases connection frequently. This results in signaling overhead in the radio network. Thus the battery consumption of the terminal increases, and the Evolved Packet System (EPS) has to take the burden of indirect cost (overhead) for processing the signaling. However, if the timer is applied in consideration of the traffic pattern per user, it is possible to use the resource efficiently and reduce the indirect cost for connection.